1. Field of the Invention
The present invention relates to a vent stringer provided in an aircraft main wing and the aircraft main wing.
2. Description of the Related Art
A fuel tank is provided in an aircraft main wing. Also, in the main wing, a vent member for introducing air from the outside into the fuel tank is provided to prevent the pressure in the tank from becoming negative when the amount of fuel in the fuel tank is decreased. The vent member also has a function of preventing the interior of the tank from becoming overpressurized at the time of refueling on the ground. The vent member has an air introducing duct on the outside of the main wing, and supplies air, which is taken in through this air introducing duct, into the fuel tank.
The vent member is provided so as to be continuous along the spanwise direction of the main wing on the inner peripheral surface side of a wing panel forming the outer surface of the main wing (for example, refer to Michael C. Y. Niu, Airframe Structural Design, Conmilit Press Ltd., 1988, p.259, FIG. 8.3.7(c)). Such a vent member includes a vent tube comprised of a tubular pipe attached to the inner peripheral surface of the main wing panel, and a vent stringer utilizing the inner peripheral surface of the main wing panel as a part of a passage wall.
As shown in FIG. 7, a vent stringer 1 is formed by attaching a channel-shaped stringer member 3 to an inner peripheral surface 2a of a wing panel 2. The stringer member 3 has a body part 3a having a hat-shaped cross section, and flange parts 3b extending to the side at an opening end side of the body part 3a. The flange parts 3b are abutted against the inner peripheral surface 2a of the wing panel 2, and are fastened to the inner peripheral surface 2a of the wing panel 2 with rivets 4 or the like fastening members. By doing this, the stringer member 3 is fixed to the inner peripheral surface 2a of the wing panel 2, whereby a passage of air introduced from the outside of the main wing into a fuel tank 5 is formed by an inner peripheral surface 3c of the body part 3a of the stringer member 3 and the inner peripheral surface 2a of the wing panel 2.
Unfortunately, the above-described configuration has a problem in terms of lightning protection. That is, the rivet 4 or the like fastening member that penetrates both the flange part 3b and the wing panel 2 is used to fix the stringer member 3 to the inner peripheral surface 2a of the wing panel 2. One end of this rivet 4 is exposed to an outer peripheral surface 2b of the wing panel 2, and the other end thereof is exposed to the interior of the fuel tank 5.
Therefore, in case of a lightning strike, an arc discharge (spark) may occur in the fuel tank 5 in the main wing through the rivet 4 or the like fastening member. Therefore, it is necessary to reliably suppress the occurrence of arc discharge in the fuel tank 5 at the time of a lightning strike.
Also, the fastening work using the rivets 4 must be performed on the inner peripheral surface 2a side and the outer peripheral surface 2b side of the wing panel 2, for example, in such a manner that a rivet material is inserted from the outer peripheral surface 2b side of the wing panel 2, and the bucking is performed on the inner peripheral surface 2a side thereof, which poses a problem that much time and labor is required.
Further, the wing panel 2 and the stringer member 3 must be formed curvedly so as to match the shape of main wing. In order to curvedly form these elements, various methods including the peen forming method have been used. In any of these methods, the wing panel 2 and the stringer member 3 must be accurately formed into a predetermined shape. However, in particular, the stringer member 3 has a hat-shaped cross section, so that the rigidity thereof is high and spring back occurs due to residual stress, and therefore it is very difficult to form the wing panel 2 and the stringer member 3 so that these elements abut on each other evenly throughout the entire contact area.